Tube production

ABSTRACT

The disclosure of this invention relates to a method and apparatus for producing tubes from billets by cold working by intermittently rotating the billets to and fro to a predetermined angle wherein the billets are first rotated a number of times in one direction throughout the cold working operation and are thereafter rotated a number of times in the opposite direction.

Elie

States Patent [191 Gerretz et al. I

' 11 3,845,649 [4 1 "Nov.5,1974

[ 1 TUBE PRODUCTION [75] Inventors: Josef Gerretz, Viersen; Paul Joeres,

Monchengladbach; Fritz Zeunert, Rheydt, all of Germany [73] Assignee: Wean United, Inc., Pittsburgh, Pa.

[22] Filed: July 5, 1973 21 Appl. No.: 376,838

[52] U.S. C1 72/189, 72/208, 72/368 [51] llnt. C1 B211) 21/06, B21b 17/00 [58] Field of Search 72/189, 197, 198, 208,

[56] References Cited UNITED STATES PATENTS 1/1912 Nowak '72/215 11/1945 Coe 7/1951 Coe 72/249 x 3,211,027 10/1965 Krause 72/208 3,274,816 9/1966 Held 3,411,336 11/1968 Wadleck 3,416,346 12/1968 Arrington 72/189 Primary Examiner-C. W. Lanham Assistant Examiner-E. M. Combs Attorney, Agent, or Firm-Henry C. Westin; Daniel Patch [5 7 1 ABSTRACT The disclosure of this invention relates to a method and apparatus for producing tubes from billets by'cold working by intermittently rotating the billets to and fro to a predetermined angle wherein the billets are first rotated a number of times in one direction throughout the cold working operation and are thereafter rotated a number of times in the opposite direction.

5 Claims, 2 Drawing Figures PATENIEUnnv 519m I 33453349 sum lUF 2 TUBE PRODUTION This invention relates to a method and apparatus for producing tubes from tube billets by cold reduction and turning. The purpose. of turning the billets is to rollthem into round form. Originally, the angle of rotation in cold reduction was about 60 of all materials being rolled. However, owing to its great economoy, the cold reduction process has in recent years been extended to substantially all materials which are to be cold-worked, for example to carbon steels and low-alloy steels, ball bearing steels, copper, condenser tube alloys, zirconium alloys and aluminum alloys. lt was found that is was necessary to depart from the original angle of rotation of 60, partly because of technological factors arising in the working and partly for reasons of the tolerance of the finished product, and angles of rotation ranging from about 30 to 90 have now been adopted.

The roll gap thickening which intially occurs at each working travel is rolled out again at the next travel by the turning of the tube billet. However, the next travel also contributes to the final rounding of the tube and to the production oif uniformity therein, more especially in regard to its internal stresses. It has been observed in the manufacture of ball bearing tubes that this uniformity of the internal stresses around the periphery of the tube can be very well produced by small angles of rotation and a progressive rotation in one direction.

it is the aim of the invention to provide a cold reduction method which has the advantage of the intermittent forward and backward rotation and of the rotation in one direction of the product. A further aim of the invention is to find a suitable apparatus by which it is possible, by means of simple design, i.'e., involving low cost of construction, to effect a rapid adaptation to change of the angle of rotation of the product. It has hitherto been very difficult to change over a machine operating on an angle of rotation of 60 to an angle of rotation of 30 because a special rotating gearing must be provided for this purpose. Steps involving complexity of construction have been necessary so that one and the same installation can be run with one and the same angle of rotation.

According to one aspect of the invention, the tube billets are first rotated a number of times in one direction, during periods when the tube and mandrel are free of the roll dies of the roll stand in first dead times between a number of rolling travels, and are thereafter turned back a number of times in the opposite direction during other free periods of the succeeding rolling strokes.

According to another aspect of the invention there is provided a cam for use in intermittently rotating to and fro tube billets, wherein the cam profile is continuous and comprises at least four circular paths, all having a common centre, each circular path being connected to an adjacent circular path by a non-circular path and wherein adjacent circular paths are at a different radius from the common center of the path.

According to a further aspect of the invention there is provided an apparatus, for producing tubes, wherein the cam is connected to a cam follower which is connected to a device for-rotating tube billets wherein on rotation of the cam the motion of the follower is transmitted to the tube billetrotating device causing rotation of a tube billet.

The invention completely obviates the thickenings occurring during rolling by repeated rotation in one direction, even with small angles of rotation, while at the same time affording the advantages of to and fro rotation.

In the preferred embodiments of the invention the tube billet can be rotated through the same angle in each instance or the tube rotated in one direction through different angles in each instance.

The tube billet can be rotated at least twice, and preferably three times, in the same direction.

The angle of rotation, or the smallest angle of rotation, can be adapted to the quality of material to be worked or to the magnitude of the forward feed, in

such manner that smaller angles of rotation are used for high-strength materials, and larger angles of rotation for softer materials and large forward feeds. The tube billet can be rotated through about 30 to at each rotation.

One type of apparatus suitable for carrying out the invention is characterized in coupling a roll stand drive to a drive of a device for the rotation of tube billetsthrough a cam disc continuously rotating synchronously with the roll stand drive. The closed cam path of the cam disc comprises at least four circular path sections associated with the center of rotation of the cam disc, which have in part different radii, and between these radii are provided transition curves which are synchronous with the periods during the reduction operation when the roll dies are free or out of contact with the tube. Through a member which explores the contour of the cam disc and which is guided in a longitudinally displaceable manner in a fixed slotted piece, the linear movement of the member is transmitted to the rotating device for the tube.

In a preferred embodiment of the apparatus according to the invention the cam disc is replaceable so that it is possible to change the angle of rotation merely by replacing the cam disc. In a further embodiment of the invention, the longitudinally displaceable member is in the form of a toothed rack, one end of which supports a cam disc roller following the cam disc path, and of which the teeth situated in the region of the other end are in engagement with the pinion of the rotating device.

It will rarely be desirable in practical operation to vary the number of rotational steps in either direction. However, experimental installations should preferably be variable in either direction, and it is therefore preferred that the drive of the cam disc should be accomplished through a change-speed gearing by means of which it is possible to change the speed ratio of the cam disc to the speed ratio of the roll stand drives.

The invention will be further described by way of example and with reference to the accompanying drawings in which:

FIG. 1 shows a cam disc with a toothed rack which is operable thereby and which is in engagement with a pinion; and

FIG. 2 shows a cam disc which is driven at one-sixth of the machine speed.

The construction illustrated in FIG. 1 comprises a cam disc 1 which is mounted on a control shaft taken from the main drive and in which a cam path 2 is cut. Bearing against this cam path 2 is a cam roller 3 secured to an appropriately mounted toothed rack 4. The toothed rack 4 is in engagement with a toothed wheel mounted on a rotatable shaft 6 of a rotatable device such as a chuck. Between the shaft 6 and the device there can be arranged a multi-speed shift gear box. By means of the rotatable shaft, the rotational movement transmitted fromthe drive cam disc 1 through the cam roller 3 and the toothed rack 4 to the toothed wheel 5 is transmitted by suitable, known means, for example through a rotary chuck to the workpiece (billet and finished tube). The transmitting means and rotary chuck along with other well-known components are illustrated in US. Pat. No. 3,344,644 dated Oct. 3, 1967, and issued to Heinz H. Fahrenholz and entitled Pilger Rolling Mills.

The manner of operation of the apparatus using a cam disc according to FIG. 2 is as follows: The cam disc 1 is driven at one-sixth of the speed of the machine. Along the path CB (angle of rotation of the cam disc), the cam roller 3 moves a distance AC, the toothed rack 4 and the toothed wheel 5 travel a distance equal to AC, whereby the workpiece is turned through a particular angle chosen to correspond to the travel AC.

If, in FIG. 2, a rotation takes place at the entry dead center or free period of the stand travel, there are obtained as the positions for the entry dead center and hence for the center of the angular range of the cam disc which is available for the lifting movement of lines XX, XY and ZZ.

Rotation of the workpiece cannot take place during the rotation of the cam disc 1 from B to F (rolling range) since the curve BF is an arc of a circle. Along the path FE of the cam roller 3, the second forward travel takes place with the lift DF, whereby the workpiece is turned once again in the same direction, through an amount corresponding to the travel DF. The curve ED is an arc of a circle, and therefore the workpiece cannot be rotated in this interval of time. Thereafter, the third forward travel takes place along the path .lH with the lift GJ, whereafter the curve HK takes place as a further arc of a circle.

Along the path KM, there then takes place the first return travel with the travel LM, i.e., the workpiece is turned back through a particular angle corresponding to the travel LM. The curve MN is again an arc of a circle, and therefore the workpiece cannot be rotated in this time. Along the path NP with the travel OP, the workpiece is again turned back through a particular angle corresponding to the travel OP. The curve PO is again an arc of a circle, because the workpiece cannot be rotated in this interval of time. Thereafter, the third backward travel takes place along the path QS with the travel RS, whereafter the curve SC is completed again as an arc of a circle.

If it is desired to operate by the method of rotation at the exit dead center or free period of the stand travel, the positions for the exit dead center must be set along the line XX, YY and 22. If it is desired to operate by the method of rotation at the entry dead center and rotation at the exit dead center, it would merely be necessary to change the cam disc 1 so that it has the same speed of rotation, but then rotates six times in the forward direction and six times in the backward direction.

If angles of rotation other than those indicated in FIG. 2 are to be used for the workpiece, it is again necessary merely to fit into the rolling mill a different cam disc having correspondingly changed lifts.

The apparatus according to the invention as described in the foregoing therefore hasthe following advantages:

I. By a simple, rapid replacement merely of the cam disc in the rotating device, it is possible to use any desired angle of rotation in the cold reduction rolling mill for the workpiece in the usual range from 30 to 90. This means at the same time that, with a particular cold reduction machine, one and the same rotating device may be employed for the whole range of angles of rotation, which constitutes a great simplification for the manufacturer of the machine and a substantial improvement and simplification of the operating conditions for the user of the machine.

2. By a simple and rapid replacement merely of the cam disc of the rotating device it is possible to carry out any desired procedure in the cold reduction, namely a. rotation at the entry dead center" b. rotation at the exit dead center, or

c. rotation at the entry and exit dead centers.

3. Substantially larger angles of rotation can satisfactorily be dealt with than the conventional ones up to a maximum of 90 degrees, since more favorable conditions exist than with a rotating device comprising a worm drive, as will be shown by the following examples.

4. Substantially higher machine speeds can be satisfactorily dealt with, and hence transmission of correspondingly greater mass acceleration forces of the masses which are to be briefly rotated.

5. By means of the alternate forward and backward rotation of the workpiece in the rotating device according to the invention, the wear on the outer rolling tools is rendered symmetrical and more uniform over the periphery of the groove, whereby the useful life of the outer rolling tools is increased.

6. The twist which is undesirable with various coldreduced materials in rolling can be avoided by employing, for example, a cam disc which gives a turning angle of 90 at a time.

A number of examples for practicing the present invention are given in the following:

1. Rolling of copper tubes.

In accordance with the present practice in the rolling of copper tubes, large billet feed advances (about 10-11 mm. per travel) are also obtained with large drawing effects (about 10-l2-fold elongation). Consequently, relatively large wall thickenings occur at the point of exit from the groove. With an angle of rotation of about 60, the danger exists that the outer rolling tools may not roll away the local wall thickenings, but will tend to turn the rolled material back into its previous position. This means that in the rolling of copper tubes it is necesssary to have an angle of rotation in the range from to in order to avoid the aforesaid effect. Moreover, as a result of the repeated rotation in one direction, any tendency to twisting is completely eliminated with an angle of less than 90.

2. Rolling of ball bearing tubes.

In accordance with the present practice in the rolling of ball bearing tubes with an angle of rotation of about 60, the rotation taking place at the entry dead center or free period of the roll stand travel, and as a result relatively great differences in the radial stresses, related to the periphery of the tube, occur as a result of this procedure. If the cold-reduced tube is divided into the individual tubing discs for the ball bearings after the cold reduction process, the danger exists, owing to possible stress differences, that the ball bearing rings may be warped, i.e., become oval within certain limits. In another method, this disadvantage is obviated by subdividing the rotation of 60 into an angle of rotation of 30 at the entry dead center of the roll stand and an angle of rotation of 30 at the exit dead center. However, this known method the rotation always takes place in one direction. If a reverse rotation were made after each rotation through 30, the ball bearing tube would not be uniformly affected over its entire periphcry, a disadvantage which is completely obviated by to tation, for example, three times in one direction and three times in the other direction.

3. Rolling of tubes from zirconium alloys.

It has been found that in the cold reduction with an angle of rotation of about 60 at the entry dead center of the roll stand, the rolled tube undergoes a certain twist in itself, which has certain disadvantages more especially in the case of zirconium alloys. These disadvantages can be obviated by the invention, namely by repeated rotation through, for example, 45 in one direction and 45 in the other direction.

In accordance with the provisions of the patent statutes, we have explained the principle and operation of our invention and have illustrated and described what we consider to represent the best embodiment thereof.

We claim:

1. A method of producing tubes from tube billets by cold reduction by a cooperative pilger mill, the steps of: I

intermittently rotating the tubes about their major axis and fro through a predetermined angle, said first rotation being one or more times in one direction and thereafter the rotation being one or more times in the opposite direction and wherein said rotation takes place during the periods of the cold reduction operation when the tubes are free of said roll dies.

2. A method according to claim 1 wherein the tube billet is rotated through the same angle in each successive instance.

3. A method according to claim 1 wherein the tube billet is successively rotated at least twice, in the same direction.

4. A method according to claim 3 wherein the tube is rotated three times in the same direction.

5. A method according to claim 1 wherein the tube billet is rotated through substantially 30 to at each rotation.

pair of roll dies of a UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. v 3 r 845 ,649 Dated November 5 19774 v Josef Gerretz et a1. Inventor(s) It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Column 1 line 7, "economoy" should read economy line 23, "oif" should read of Column 3, line 5, drive" should read w driven line 27 "XY" should read YY 7 line 36, "EDf' shouldread EJ m. Column 6, line 8,

taxis and fro should read aa cis to and fro Signed and sealed this "4th day of February 1975.

(SEAL) Attest:

McCOY u. 'GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM'DC 60376-P59 U.S. GOVERNMENT PRINTING OFFICE 5 59 9 FORM PC4050 (IO-69) 

1. A method of producing tubes from tube billets by cold reduction by a cooperative pair of roll dies of a pilger mill, the steps of: intermittently rotating the tubes about their major axis and fro through a predetermined angle, said first rotation being one or more times in one direction and thereafter the rotation being one or more times in the opposite direction and wherein said rotation takes place during the periods of the cold reduction operation when the tubes are free of said roll dies.
 2. A method according to claim 1 wherein the tube billet is rotated through the same angle in each successive instance.
 3. A method according to claim 1 wherein the tube billet is successively rotated at least twice, in the same direction.
 4. A method according to claim 3 wherein the tube is rotated three times in the same direction.
 5. A method according to claim 1 wherein the tube billet is rotated through substantially 30* to 90* at each rotation. 